DESCRIPTION: Bone morphogenetic protein 5 (BMP-5), a morphogen and bone growth factor, is a member of the TGFb superfamily. The short-ear (Se) mouse mutants have been linked todeletions in the BMP-5 gene. In addition to numerous cartilage defects, Se animals exhibit a variety of skeletal defects, including shorter wider skull, missing or reduced vertebral processes, missing 13th pair of ribs, bifurcation of xiphoid process, loss or reduction of sesamoid bones, altered curvature of long bones, and deficient repair of rib fractures. The fracture callous in Se animals is smaller than normal and produces less bone and cartilage. In the present studies, Se animals will be used to study the effects of BMP-5 deficiency on induced alveolar bone remodelling. Remodelling systems induced by orthodontic tooth movement, tooth extraction socket healing, and tooth hypereruption following extraction of the opposing tooth will be analyzed. Various histomorphometric parameters of bone remodelling will be quantified, including number and types of osteoblasts, number of osteoclasts, osteoblast and osteoclast surface, Howship's lacunae, osteoid surface, wall width, and mineral apposition rate. Only three animals/group will be analyzeddue to the laborious nature of the histomorphometric analyses. Gross differences only will be evaluated. The relationship of changes in these parameters to the genotype/phenotype of mutant animals will be analyzed statistically. The goal is to evaluate the use of various Se mutations for studying the effect of BMP-5 on bone remodeling.